I've been thinking about homeschooling for my senior year and I was wondering how I would go about doing it. Is it necessary to have a teacher or could I create my own curriculum? Also, would it be acceptable to just take standardized tests for various subjects to earn a high school diploma?

You can create your own curriculum and issue yourself a high school diploma, so long as you complete the required course material for high school graduation in your state (plus any necessary prereqs for the college you want to go to...) and can prove competency through a portfolio of work and/or series of standardized tests. Of the two options, the latter is better, since it's less work for colleges to take score A and compare it to score B than it is to read through your portfolio of work and try to figure out if you covered everything properly. It's also less work for you.

If you can, take CLEP exams, they're widely available and done on computers now, so you don't have to write everything by hand like on AP exams. AP or DSST will work for if there isn't a CLEP available, or if the particular subject involves a lot of hand work (Calculus, for instance).